Internet Explorer:

Click on 'tools' then 'Internet Options'...
In the 'General' section click on 'Accessability'...
then check 'Ignore font sizes' and finally, click 'ok'.

You can then change text sizes in the normal way....
click 'View' then select 'text size'.

Firefox

Click on 'Tools' then 'Options'. Select the 'Content Tab' make sure the 'Enable Javascript Box' is checked then click 'advanced'. Uncheck the box marked 'Allow pages to choose their own fonts....'

Pages will then use your default fonts and sizes.